生长激素受体基因表达的研究进展

生长激素(growth hormone,GH)在促进动物生长、发育等代谢过程中起着重要作用。长期以来人们在研究动物生长发育机制及其调控时,主要着眼于提高生长激素水平。然而GH必须与靶器官上生长激素受体(growth hormone receptor,GHR)结合,由GHR介导将信号传入细胞内才能发挥作用。大量研究结果显示,动物生长速度与GH水平并不完全平行,但与肝脏GHR呈明显正相关。生长快的肉鸡血液中GH和垂体GH mRNA水平比生长慢的蛋鸡低,而肝脏GHR水平比蛋鸡高;患侏儒症动物血液中GH浓度却比正常动物高,而GHR胞外部分缺失或功能不全。可见GHR基因表达对动物生长发育调控起着至关重要的作用。     

孕激素诱导的生长激素与犬的乳腺肿瘤

乳腺肿瘤是犬的最常见的肿瘤，约占母犬肿瘤总数的一半；乳腺肿瘤约有一半是恶性肿瘤，发生转移的比率很高。犬乳腺肿瘤的发病原因还不很明确，它的形成都受哪些因子调节还未完全确定。孕激素能够诱导乳腺组织生成并蓄积生长激素，使乳腺增生，最终导致犬乳腺肿瘤的形成。在此过程中，雌激素受体、孕激素受体、生长激素结合蛋白和生长激素受体在乳腺癌的形成、发展中起关键作用。从内分泌的角度对犬乳腺肿瘤发病机理作了简单综述，以期为激素治疗乳腺肿瘤提供一些理论依据。     

不同泌乳相关激素和生长因子对奶牛乳腺上皮细胞增殖的影响

本研究旨在探讨不同泌乳相关激素和生长因子对奶牛乳腺上皮细胞增殖的影响及其与细胞外基质主要成分层黏连蛋白的关系。将正常的荷斯坦泌乳期奶牛乳腺上皮细胞进行体外培养,在未包被或包被层黏连蛋白的条件下,以MTT法检测催乳素(PRL)、牛生长激素(GH)、类胰岛素生长因子-1(IGF-Ⅰ)、类胰岛素生长因子-2(IGF-Ⅱ)对细胞增殖作用的影响。在层黏连蛋白包被条件下,进行血清恢复的同时添加不同泌乳相关激素和生长因子,GH、IGF-Ⅰ有促进细胞增殖的作用(P<0.05),PRL、IGF-Ⅱ有维持细胞存活的作用(P<0.05);无血清时,几种激素和生长因子单独添加均无明显促增殖效应(P>0.05)。无基质条件下,与血清联合使用时,PRL、GH、IGF-Ⅰ、IGF-Ⅱ均对细胞生长有不同程度促进作用(P<0.05);无血清时,仅IGF-Ⅰ使细胞增殖速率显著加快(P<0.05)。层黏连蛋白作为培养基质对于体外培养的泌乳乳腺上皮细胞生长速度没有显著促进作用,但有利于PRL和IGF-Ⅱ发挥促存活作用。PRL、GH、IGF-Ⅰ、IGF-Ⅱ对细胞增殖和存活有促进作用,但需要与血清中其他成分协同才能充分发挥作用,其中IGF-Ⅰ促增殖能力最强。     

生长激素受体介导的信号转导机制研究进展

生长激素(growth hormone,GH)对动物的生长发育具有重要的生理作用.GH与生长激素受体(growth hormone receptor,GHR)结合后才会发挥一系列的生理作用.近年来,人们对GHR结构和功能的研究取得了巨大的进展,并取得了一些重大的突破.现在已清楚了GH-GHR轴激活一些相关的信号转导通路,但并非所有的通路都依赖酪氨酸激酶.作者从以下几个方面总结了GHR作用下的信号转导机制的研究进展:GHR的结构与功能;依赖JAK2的相关信号通路;不依赖JAK2的相关信号通路;GHR信号负调控因子.阐明这些复杂机制,对进一步了解GH对动物不同的生理和病理作用具有重要意义.     

Growth hormone suppresses the expression of IGFBP-5, and promotes the IGF-I-induced phosphorylation of Akt in bovine mammary epithelial cells

Growth hormone (GH) plays a specific role to inhibit apoptosis in the bovine mammary gland through the insulin-like growth factor (IGF)-I system, however, the mechanism of GH action is poorly understood. In this study, we show that GH dramatically inhibits the expression of IGFBP-5, and GH along with IGF-I enhanced the phosphorylation of Akt through the reduction of IGF binding protein (IGFBP)-5. To determine how GH affects Akt through IGF-I in bovine mammary epithelial cells (BMECs), we examined the phosphorylation of Akt in GH treated BMECs and found that IGF-I induced phosphorylation of Akt was significantly enhanced by the treatment with GH. We demonstrated that GH reduces mRNA and protein expression of IGFBP-5 in BMECs, but it does not affect the expression of IGFBP-3. To determine that the enhanced effect of the Akt phosphorylation by the treatment of GH is due to the inhibition of the expression of IGFBP-5, we examined the effect of IGFBP-3 and -5 on the phosphorylation of Akt through IGF-I in the GH-treated BMECs. The phosphorylation of Akt was inhibited in a dose-dependent manner when IGFBP-5 was added at varying concentrations and was also inhibited in the presence of IGFBP-3. The results of this study suggest that GH plays an important role on mammary gland involution in bovine mammary epithelial cells.     

鸡生长激素受体胞外区原核表达分析

生长激素与其靶细胞膜表面的生长激素受体(GHR)结合,可以促进动物生长发育和调节新陈代谢。为获得鸡GHR蛋白,试验通过PCR扩增获得GHR胞外区序列。经双酶切后连接入原核p ET-32a(+)表达载体,构建了鸡GHR胞外结构域的原核表达载体。将该重组质粒转入E. coli BL21(ED3)表达菌株。通过IPTG诱导其表达GHR重组蛋白,并探讨不同IPTG浓度、诱导时间和诱导温度等条件对鸡GHR重组蛋白表达的影响。结果表明:诱导GHR重组蛋白表达的最适条件为IPTG终浓度2.00 mmol/L、诱导时间为4 h、培养温度为37℃,在此条件下,GHR重组蛋白表达量最高。研究结果为后续GHR抗体制备奠定了基础。     

Role of progestin-induced mammary-derived growth hormone in the pathogenesis of cystic endometrial hyperplasia in the bitch

Endogenous progesterone and synthetic progestins may induce hypersecretion of growth hormone (GH) of mammary origin, hyperplastic ductular changes in the mammary gland, and the development of cystic endometrial hyperplasia (CEH) in dogs. It was investigated whether progestin-induced mammary GH plays a role in the pathogenesis of CEH in the bitch. During 1 year, bitches with surgically excised mammary glands and healthy control bitches received medroxyprogesterone acetate (MPA). Before and after MPA treatment, uterine and mammary tissues were collected for histological, immunohistochemical, and RT-PCR examination. After MPA administration, the mammary tissue in the control dogs had differentiated into lobulo-alveolar structures and CEH was present in all uteri of both dog groups. In the MPA-exposed mammary tissue of the control dogs, GH could only be demonstrated immunohistochemically in proliferating epithelium. After treatment with MPA the dogs of both groups had immunohistochemically demonstrable GH in the cytoplasm of hyperplastic glandular uterine epithelial cells. RT-PCR analysis of the mammary gland tissue after MPA administration demonstrated a significant higher GH gene, and lower GHR gene expression than before treatment. In the uterus, the expression of the gene encoding for GH was significantly increased in the mastectomized dogs, whereas in the control dogs the expression of the gene encoding for insulin-like growth factor-I had significantly increased with MPA administration. MPA treatment significantly down regulated PR gene expression in the uterus in both dog groups. These results indicate that progestin-induced GH of mammary origin is not an essential component in the development of CEH in the bitch.     

Involvement of connective tissue growth factor (CTGF) in insulin-like growth factor-I (IGF1) stimulation of proliferation of a bovine mammary epithelial cell line

The objective of this study was to determine the mechanism by which insulin-like growth factor-I (IGF1) stimulates proliferation of mammary epithelial cells, using the bovine mammary epithelial cell line MAC-T as a model. IGF1 significantly up- or down-regulated the expression of 155 genes in MAC-T cells. Among the most significantly suppressed was the gene for connective tissue growth factor (CTGF), a secretory protein that has both proliferative and apoptotic effects and is also a low-affinity binding protein of IGF1. IGF1 inhibited CTGF expression through the PI3K-Akt signaling pathway. Administration of growth hormone (GH), a strong stimulator of IGF1 production in vivo, decreased mammary CTGF mRNA in cattle; however, GH did not affect CTGF expression in MAC-T cells, suggesting that IGF1 may also inhibit CTGF expression in the mammary gland. Added alone CTGF stimulated proliferation of MAC-T cells, but in combination with IGF1 it attenuated IGF1's stimulation of proliferation of MAC-T cells. Excess IGF1 reversed this attenuating effect of CTGF. Despite being an IGF binding protein, CTGF did not affect IGF1-induced phosphorylation of IGF1 receptor (IGF1R) or IGF1R expression in MAC-T cells, indicating that the attenuating effect of CTGF on IGF1 stimulated proliferation of MAC-T cells was not mediated by decreasing IGF1's ability to bind to IGF1R or by decreasing IGF1R expression. Overall, these results suggest a novel biochemical and functional relationship between CTGF and IGF1 in the bovine mammary gland, where IGF1 may inhibit CTGF expression to reduce the attenuating effect of CTGF on IGF1 stimulated proliferation of epithelial cells.     

玉米赤霉烯酮对青年母猪子宫发育、生长激素分泌及其受体分布与表达的影响

本试验旨在研究玉米赤霉烯酮(ZEA)对青年母猪子宫发育、生长激素(GH)分泌及其受体(GHR)分布与表达的影响.选择胎次和体重[(23.20±0.68)kg]相近的长×大二元青年母猪48头,将其随机分为4组,每组12个重复,每个重复1头.对照组(CON组)饲喂基础饲粮,试验组(T1、T2、T3组)饲喂在基础饲粮中分别添...     

The role of IGFBP-5 in mammary gland development and involution

Insulin-like growth factor-I (IGF-I) plays an important role as a survival factor during mammary gland development and remodelling during involution of the mature/lactating mammary gland, and elevated concentrations have been associated with increased risk of breast cancer. The actions of IGF-I are modulated by a family of binding proteins (IGFBPs) and we have shown that IGFBP-5 is associated with cell death in the mammary gland and more recently provided the first evidence that it is causally related to apoptosis of the mammary gland. A transgenic mouse expressing IGFBP-5 on a mammary-specific promoter led to impaired mammary development involving inhibition of IGF-signalling and involving members of the Bcl-2 family. Subsequent studies in vitro and in vivo using exogenous IGFBP-5 treatment have added support to this concept. Although the effects of IGFBP-5 did appear to involve inhibition of IGF action, a role for IGF-independent effects cannot be ruled out. Such IGF-independent effects involve potential interactions with components of the extracellular matrix involved in tissue remodelling including plasminogen activator inhibitor-1 (PAI-1). In addition, intracellular events involving nuclear localisation of IGFBP-5 have been shown to have the ability to inhibit cell proliferation. Thus, IGFBP-5 seems important for regulating both apoptosis and cell proliferation in the mammary gland during development and post-lactation involution.     

miR-138对小鼠乳腺发育及泌乳功能的影响

microRNAs(miRNAs)在各种类型细胞增殖、分化和凋亡中发挥了重要作用。miR-138参与乳腺发育周期过程中细胞增殖分化的调控。试验以小鼠为动物模型,尾静脉注射miR-138基因抑制剂,应用幼鼠体重称重法,检测miR-138抑制后乳腺泌乳量变化;应用电子显微镜等技术观测乳腺组织形态变化,抑制miR-138后,小鼠乳腺上皮细胞增加,乳汁分泌量增加;抑制miR-138后,观察小鼠乳腺组织超微结构可发现,乳腺细胞的代谢活动增强;收集尾静脉注射miR-138 抑制剂的小鼠乳汁,检测发现其乳糖、乳中酪蛋白含量均有所增高。研究认为,miR-138可刺激乳腺上皮细胞增殖,增加乳腺发育泌乳过程中乳的分泌,并且调控乳汁中重要成分含量。     

Insulin receptor is expressed in normal canine mammary gland and benign adenomas but decreased in metastatic canine mammary carcinomas similar to human breast cancer

Insulin receptor (INSR) or insulin-like growth factor (IGF) signalling is speculated to be involved in mammary tumour development. Expression levels of members of the insulin receptor family (INSR, IGF1R, IGF2R, GHR) and their ligands IGF1and IGF2 were quantified in macro- and microdissected tissue samples of normal canine mammary gland, adenomas, carcinomas and their lymph node metastases to evaluate their potential impact on the carcinogenesis of canine mammary tumours. Normal mammary gland and adenomas had strong INSR expression, while carcinomas and metastases had significantly decreased expression. No differences were observed for IGF1R expression. IGF1, IGF2 and GHR mRNA expressions were strongly decreased in adenomas, carcinomas and metastases. INSR and IGF1R are therefore expressed in normal gland and adenomas and an increased stimulus by their ligands may be a proliferative stimulus in those tissues. However, decreased INSR expression carcinomas and their metastases render questionable its impact at late stages of carcinogenesis.     

Evidence of a Direct Role for Growth Hormone (GH) in Mammary Gland Proliferation and Lactation

A panel of monoclonal antibodies to the growth hormone (GH) receptor/binding protein was used to demonstrate the existence and detail the expression of GH receptors in ductal and alveolar epithelial cells from rat and rabbit mammary glands by immunohistochemistry. Intense immunoreactivity was present in membrane, cytoplasm and some nuclei of epithelial cells during proliferation and lactation. Receptor expression decreased during weaning and was absent or weak in regressive mammary glands. Immunoreactivity was weak in ductal epithelial cells from virgin adult animals. Pronounced expression of GH receptor/binding protein was observed with two monoclonal antibodies and lesser reactivity was seen with others, paralleling their affinities for the receptor. The cytoplasmic presence of this putatively plasma membrane located GH receptor is accounted for by the existence of a soluble form on the GH receptor, namely the growth hormone binding protein derived from the membrane receptor by cleavage. Primary localization of the receptor in proliferating and lactating epithelial cells suggests that the rat and rabbit mammary gland is a GH target tissue. This finding is in contradiction to both classical GH action and the somatomedin hypothesis and challenges the widely held view that GH has no direct influence on mammary growth and function.     

Hormone interactions confer specific proliferative and histomorphogenic responses in the porcine mammary gland

Mammary gland growth and morphogenesis are regulated by interactions between hormones as much as by their individual actions. The effect of these interactions on the mammary gland phenotype in species other than rodents is relatively undefined. We investigated the individual and combined effects of estrogen (E), progestin (P), and prolactin (PRL) on mammary gland development in gilts. Pigs were shown to have a ductal-lobular parenchyma that underwent hormone-stimulated progression of terminal ductal lobular unit (TDLU) morphogenesis similar to that in the human breast. Ovariectomy plus hypoprolactinemia abolished mammary gland growth. Estrogen alone stimulated mammary epithelial cell proliferation, terminal bud formation, and the progression of TDLU1 structures to a TDLU2 morphotype. Maximal epithelial cell proliferation, DNA content, parenchymal area, and morphological development of the porcine mammary gland were realized following treatment with E + PRL or E + P + PRL. In contrast, P alone did not promote epithelial cell proliferation, TDLU type progression, mammary gland growth, or morphogenesis. These data indicate that interactions between E and PRL are the main determinants of growth and morphogenesis in the porcine mammary gland.     

动物生长轴中STAT调控胰岛素样生长因子Ⅰ 表达的研究进展

IGF-Ⅰ能够促进细胞的增殖分化和代谢过程,而其表达是受STAT介导的,该通路最终受到生长激素(GH)的调控。生长激素与生长激素受体结合激活JAK家族,使得STAT家族成员,特别是STAT5磷酸化。磷酸化的STAT5进入细胞核内,与IGF-Ⅰ基因上的STAT5结合位点结合,激活胰岛素样生长因子-Ⅰ(IGF-Ⅰ)的表达,IGF-Ⅰ再通过血液循环到达机体的局部组织,促进组织细胞的生长和分化。作者对动物生长轴中STAT和IGF-Ⅰ的组成、功能以及STAT调控IGF-Ⅰ表达的分子机理的研究进展作一综述。     

动物乳腺干细胞的研究进展

乳腺干细胞具有产生所有类型乳腺细胞的能力。在乳腺组织生长发育过程中,乳腺干细胞对于动物青春期、妊娠期、泌乳期和泌乳衰退期的乳腺生长与重建等具有重要意义。体外培养的乳腺干细胞是研究乳腺细胞增殖、分化、生存和凋亡等信号通路的理想模型,同时在转基因乳腺生物反应器方面也具有重要的应用前景。因此,乳腺干细胞的研究对于乳腺发育的认知,乳腺癌的治疗及农业生产具有重要意义。作者针对乳腺干细胞的筛选、定位和体外培养方法的研究现状进行了系统的综述,并对未来的研究方向与应用前景加以展望。     

生长激素激活受体机理的研究进展

生长激素(growth hormone,GH)是一种含有191个氨基酸的多肽类激素,分子质量为22 ku,由垂体前叶分泌进入血液循环,与靶细胞膜表面以二聚体形式存在的生长激素受体(growth hormone receptor,GHR)相结合。对于受体的激活来说,仅是二聚化还不够,还需在GH的诱导下发生构象变化,进而才能诱发Janus激酶2(Janus kinase 2,JAK2)的酪氨酸磷酸化,并通过4条不同的路径将信号传入细胞内,从而发挥代谢、增殖及分化等一系列生理效应。作者就生长激素与受体的结构、作用机理、信号转导通路的进展进行综述。     

抗生长激素受体单克隆抗体的功能特点

The growth hormone receptor (GHR) is the key regulator of postnatal growth which belongs to the type Ⅰ cytokine receptor that mediates many functions regulated by growth hormone (GH). Monoclonal antibodies (mAb) to the GHR have been important tools for the study of this receptor. All these anti-GHR mAbs, designated 1H2, 1A9, 2C3 and mAb263, are highly reactive with GHR, but 1A9 does not promote growth in hypophysectomized rats, 2C3 can do and this effect will be inhibited in the presence of GH. mAb263 as the commercial monoclonal antibody that binding to the receptor has a similar effect with GH, not only can recognise GHR,but also can induce a conformational change of the receptor in a similar manner, but not identical with GH.     

Positive effect of silymarin on cell growth and differentiation in bovine and murine mammary cells

Silymarin, a naturally acknowledged hepatoprotector used in humans to treat liver diseases has been tested in murine (HC11) and bovine (BME‐UV) mammary epithelial cell lines to evaluate a possible direct effect on cell growth and differentiation in mammary gland. Silymarin enhanced cell proliferation (p < 0.05) from 10 to 1000 ng/ml in association with growth factors, (up to 20%) or alone (up to 15%) versus controls. Furthermore, silymarin (100 ng/ml) was able to increase (p < 0.05) β‐casein gene expression alone or in association with prolactin (5 μg/ml). These effects may be related with protein kinase B (AKT) activation induced by silymarin treatment (p < 0.05) and/or by a dose‐related inhibitory effect (p < 0.05) on caspase‐3 activity related to a protective role in cell apoptosis. These data suggest that silymarin should be considered a candidate to support mammary gland activity during a lactogenetic state.